Over the years I can't count the number of times the subject of "How to add Weight & Body" to the music has been discussed on this Forum. I know because since purchasing my original Decware Zen Select over 12 years ago I have read all of these posts with interest in doing the same. In almost 35 years of listening to Rock and Blues I have used a variety of subwoofers to augment the low end.

My main interest is music and for years I've seen a lot of bands locally (couple times a month normally). Can't beat sitting 30 feet from the band while tapping your toes to that awesome bass line. Each pluck of the bass guitar distinctly audible and clean, thinking why can't I make it sound that great at home?

Until recently I've always blamed it on poor recording technique, poor mastering, poor room acoustics and a variety of other excuses. That is until I ordered the MBM-12 MK2 Mid Bass Module from HSU Research last spring: http://www.hsuresearch.com/products/mbm-12mk2.html

After lots of research I was still skeptical, kind of like 12 years ago when I ordered my Decware Zen Select: 2-watts, yea right, does that come with a can of snake oil and bag of pixie dust too ??? Long story short, I soon sold all my solid state gear and have listened to the little Zen all these years until replacing it a couple months ago with the Super Zen.

So against my better judgment and based on everything I thought I knew about audio and subwoofers, I hit the purchase button. Just like Decware, HSU has an no questions asked return policy so I'll have a little fun, maybe learn something and send it back right ???

Well it's 8 months later and I'm still amazed at what the MBM-12 adds to the music presentation. Each bass note is clean and distinct. Drums really pop !! Actually I have two and run them in stereo, one located next to each of my mains. One is great, it gives you about 85% of what two will do in a large listening room.

I have full range Klipsch RF-7 mains connected directly to my Super Zen (running full range signal). The MBM-12 is connected to the Super Zen via speaker level connection also operating in what HSU calls "Augmentation Mode". So the mains and MBM-12 are both reproducing the signal below 150 Hz down to around 50 Hz.

Now I know there are a Zillion technical reasons that can be cited as to why there is no way this can possibly work, or at least sound good. Even HSU considers using speaker level connections and operating in "Augmentation Mode" as their least desirable connection and set-up method. All I know is it's hard to dispute what I'm hearing, so I'm just going to enjoy the music !!

When I purchased the Super Zen things got even better. The Super just seems to have much better resolution across the board and especially on the low end compared to the 12 year old Select with no mods. Lots of Weight & Body for all day listening without having to crank it to the edge of clipping. And when you do crank it up, well it is just GREAT !!! No more wishing I had just a couple more watts. For the most part I now listen at lower volume levels because as I turn that volume knob up I just reach that "Satisfaction Point" sooner.

The HSU MBM-12 (Mid Bass Module) has been a great $500.00 investment for me. I also have the HSU ULS-15 15" sealed subwoofer which is a great product also (the best of many subs I have owned). I have listened to music with the MBM-12 only and the ULS-15 only. If you told me I could only have one, then I would say hands down keep the Mid Bass Module.

Augmenting the mid bass region has that much of a positive impact on music. There is simply more going on in most music between 150 & 50 Hz then below 50 Hz. Obviously the ULS-15 tops it all off if your budget allows. If however you are on a tight budget or simply looking to add a substantial bit of "Weight, Body & Punch" on the lower end you owe it to yourself to audition the MBM-12.

interesting...I run taboo with vcap & hazen mod and old zen select with hazen mod..also use zen tube buffer plus Monarchy audio dip...one classic and other 24/96...I buy them used and find that they boost sound and increase base...with decware outboard dac and Lars audio equivalent I find that my sound is smoother and less digital (harsh). It's a pretty cheap way to improve sound.I have a smaller listening room and listen mostly to jazz so these minor tweeks fit my listening environment well.

Thanks DBC! I wrote a question to you over in the SUPERZEN AND Z-STAGE thread. You just answered all for me. Thanks again for your insight on this. I am going to try this module. I now have a room where I can stretch the legs of my Super Zen CKC to obtain more dynamics-not-just tone and texture that I have enjoyed over the years with the SE84CS and now CKC. My Zu Union's in Sangria Red arrive next week! -Stone

As you probably gathered from my original post I have a Pair of HSU ULS-15 subs. If I'm not mistaken ULS stands for "Ultra Linear Sealed". So these have no ports. Before my purchase I called HSU Research and Dr. Hsu answered the telephone himself on about the third ring. He told me the ULS-15 was their most accurate sub for music but that the VTF-15 was very close. VTF for "Variable Frequency Tuning" . You have the option to run sealed or vented with the VTF Sub series as you know.

At that time I was looking to replace my 13 year old 18" Velodyne sub. I purchased the pair of ULS-15's which is overkill in some respects. The main benefit of the pair is more uniform bass throughout the listening space.

When the ULS-15's arrived I wheeled the old Velodyne out and the ULS-15's in and powered everything up. That moment was similar to powering up my Super Zen for the first time. WOW, this is a real improvement right out of the box !!

I had the ULS-15's for a couple months before I ordered the pair of MBM-12 MK2 (Mid Bass Modules). I was so impressed with the ULS-15's I wanted to see what Dr. Hsu's mid bass module would do in a music system. Interestingly HSU does not really advertise the MBM as a music product. I get the impression they are pretty much in the digital multi-channel universe (like most). While talking to Dr. Hsu about my tube set-up I kind of got the feeling he was thinking "Why don't you just buy a good $400.00 multi-channel AV receiver?". It was a bit funny.

An interesting side note from this same conversation with Dr. Hsu. He stated that tube amps typically have somewhat poor low frequency response compared to Solid State. I didn't think much about that comment again until I powered up my new Super Zen and realized how much cleaner and more defined the low end was.

So when it comes to the Mid Bass Module I'm not really using it exactly as the nice folks at HSU envisioned. As you know from looking at the HSU site, the Mid Bass Module is basically the same design concept as their VTF (Variable Tuning Frequency) sub line. Difference being it is specifically optimized to reproduce the 150 to 50 Hz frequency range.

You can run the MBM in Sealed or Vented mode. I have listened extensively in both modes. Since getting the Super Zen I can say I prefer the Sealed mode for music. In the Vented mode drums have a bit more slap but low bass guitar notes on some recordings can sometimes get a little "Wooly". Just seems like I can play just about any material in the Sealed mode and it sounds good if not great.

So as I said in my original post, if I were forced to choose only one, I would opt for the Mid Bass Module over the ULS-15 sub as best audible improvement and bang for the buck. I listened to a couple Door's CD's this morning with MBM only and then Sub only to confirm my earlier impressions and statement in this regard.

HSU makes some fine products. Problem is if you try the MBM i think you will like it. Worse yet, the MBM will likely leave you thinking "What would it sound like with one of their subs?".

I have two ULS-15's and two MBM's. I know that is a little over the top. I have run the set-up using one ULS-15 and one MBM and there is not much more a sane person could ask for if they just had one of each.

In my case I am running these in stereo (left Sub & MBM left channel only, right Sub & MBM right channel only). I posted a couple pics in the Member's Picture Gallery. Sorry for the poor quality, just into music more than photography and interior decorating. Room is approx 15 feet wide by 21 feet long with an equally large adjacent dining and kitchen area.

Having twin subs and twin MBM's does a lot to produce even bass through the listening room and quite frankly the whole house. I realize this is not a practical set-up for most working folks with real lives to live.

You might think by looking at the system that I'm some type of Freakish Bass Head in need of serious help. Well I'm not into Bass simply for the sake of Bass. I like smooth distinct audible bass that is not in your face but rather contributes to the overall presentation. On the other hand Black Sabbath and Michael Jackson really do kick out the Bass on their recordings.

A good solid Bass foundation gives the impression the whole system is playing MUCH louder. I would describe the Bass as Effortless, and it does not get in the way of other instruments or vocals. Even at low volume the bass has a real physical presence. As a result I tend to listen at lower volume levels with a great deal of satisfaction.

I was just looking at the HSU ULS-15 sub, thinking of getting a single one, with the general idea that the larger sub I can get, the better off I'll be for full bass reproduction. I wanted a sealed sub, but your statement that you preferred the MBM over the ULS if you had to choose one surprised me.

Can you expand on this? Any idea why a smaller sub would add more weight than the larger one? Is it related to your speakers frequency response perhaps? Placement of the ULS vs the MBM? Very curious to hear why you like the MBM better. I do have to choose only one, so any insight would be great. Thanks,

You ask a great question. I have to say going in to this (experimentation with the MBM) my past experience and preconceived notions on what I thought I knew about subwoofers was actually an impediment. After all if you know the world is flat then you are unlikely to set sail for the horizon.

A little background. My Klipsch RF-7 mains are full range speakers. I've been to the local Klipsch dealer and when they crank them up with 200 Solid State Watts per channel they can kick out the bass. Problem is you have to play them loud and your ears start to bleed from the Solid State highs after about 5 minutes.

Come home crank the RF-7's with my Super Zen 2 Watts per channel and the mids and highs are to die for at normal listening levels. But where's all the Bass ?? I can hear it but it's a little faint for my liking. Well lets crank it up some more and I start to drive the Super Zen into clipping.

No problem, I've got the HSU ULS-15 (15 inch sealed sub) tucked into the front right corner of my listening room. Turn that baby on and set the crossover at 90 Hz (max crossover setting on this sub). Yuck, it's boomy. Darn I've got a room induced peak at around 70 HZ. Turn the sub volume down from 50% to 20% and no more Boom, in fact pretty much no more nothing.

OK lets set the crossover at 50 Hz and the volume back to 50%. That sounds really good with Black Sabbath, Nickle Back and other music with lots of low bass (hey lets start spinning some RAPP) not really. Does not do much for The Rolling Stones though ??? OK Lets move the sub to the Front Left Corner. Darn, I've got a peak around 45 Hz there.

OK let's move the sub more to the center of the room along the front wall. Not too bad. I have the sub volume at 50% and crossover set at 90 Hz (max). I'm listening at a comfortable level, Super Zen sounds good and the music has a little meat on it's bones, I like it. Lets see if there is more of that to be had, tweak the sub volume up to 55%. What happened ?? That does not sound natural. OK, sub volume back to 50%. I like what I'm hearing but wish I could get some more of that. Another point, now that the sub is in the center of the front wall I don't have the really low 20 Hz extension on movies ??

OK, fast forward to today. Having used the MBM (mid bass module) for months now I can appreciate how much music material lies between 50 and 150 Hz (150 Hz max crossover setting on the MBM). I don't think it was a mistake that Dr. Hsu designed and optimized to MBM to accurately reproduce material in this range. If you read some of Dr. Hsu's material he states below 50 Hz you need a big heavy driver and above 50 Hz a smaller lighter driver is optimal.

My Theory: You have a sub reproducing low frequency up to 100 Hz as an example (assuming no room induced peaks, good luck on that). As you increase the the sub volume at some point your brain says there is a disconnect between everything below 100 Hz which is going up in volume and everything above 100 Hz which is not going up in volume because the mains are producing that portion.

As you increase the volume on the MBM the frequency range that Dr Hsu felt was important (50 to 150 Hz) increases across the board as opposed to my example above using a single subwoofer and the mains.

I have to admit I was sure there would be a conflict to deal with given that my mains go down to 40 Hz. Certainly the MBM and Mains reproducing the same frequency range was going to be a problem. Well I run the MBM crossover at 150 Hz (max) and there is no issue. Basically just keep increasing the MBM volume until you brain says that's not right. Back the MBM volume off just a tad and enjoy.

Now will a system with a single MBM benefit by introducing a good sub, well yes. For reference I would say 80% of the performance bang comes from the MBM. Add a good subwoofer and you can increase performance (Weight & Body) another 20%. I think this goes right back to the fact that most music material does not have a lot going on below 50 Hz.

Recap:

Best room location for a box to reproduce frequencies below 50 Hz is often not the best location for a box to reproduce frequencies above 50 Hz.

Best driver to reproduce frequencies below 50 Hz is not the best driver choice to reproduce frequencies above 50 Hz.

Listening using a single MBM as opposed to a single Subwoofer there is a whole lot more going on in the bass region above 50 Hz then below on most music material. Therefore IMHO using a single MBM has a more profound impact on the overall "WEIGHT & BODY" of the overall presentation.

Dr. Hsu knew something I didn't when he decided to build a box optimized to reproduce frequencies between 50 and 150 Hz.

The new Super Zen heightens the performance of the MBM compared to my 12 year old stock Zen Select. Point being if your source or amp are a tad muddy on the low end that will be reproduced by the MBM.

Final Thought: Prior to receiving the Super Zen I had a tendency to tinker with the MBM module volume. With better more modern recordings it seemed I could run the volume a tad higher without the MBM calling attention to itself. Older material could get a tad muddy so I would tweak the volume down a tad. Since introducing the Super Zen I have not touched the MBM volume. I think this is due to the Super's improved low end clarity and separation.

My apologies for the long winded response. If anyone does manage to get this far then I hope it was of some help.

I have to say that there is a lot that I agree with about your experience with bass frequencies. All rooms lie in some fashion when it comes to bass. Placement is really the best way to achieve most of what can be done. I also use a Velodyne SMS-1 to help with the process. Your point about different sized drivers used to reproduce low(below 50hz) and bass(50-150hz) sounds like a very good idea. It doesn't help my wanting to keep a system as simple as possible, but then things should be kept as simple as possible, but not simpler(Einstein said it right). On a different note, I have always liked the folded bass horn for the power and purity. I built a K-horn sold by Speakerlab when I was in high school. Though it definitely wasn't a Klipsch, it gave me an idea what bass could be.

I agree with your comment regarding simplicity. Take my system for example; without the subs it is pretty basic which is always good. Source, pre, amp, mains.

The intent of my original post was to suggest that if someone has a simple system and would like to add a noticeable amount of quality "Weight & Body" to the overall presentation that a single HSU Mid Bass Module is a simple and effective option based on my experience.

I wanted to comment on placement also. The MBM is not all that sensitive to placement. With one unit you would want it somewhere along the front wall center or slightly off center depending on what your arrangement allows. Corners are not the best choice since at these frequencies you may start to sense that most of the bass is coming from one side of the sound stage.

As long as the subject is subwoofers, I'd like to know people's opinion about something I was thinking of doing:

I wanted to augment the sound of my Tang Band full range back horn loaded speakers, and a mini sub would do just fine... The only thing is, no sub out on my Zen amp... I do, however, have a Zen CD player, and I was wondering if I could use the standard [op amp] outputs on the CDP to feed the sub... I mean, they are supposed to be live... ???...

If a rabbit defined intelligence the way man does, then the most intelligent animal would be a rabbit, followed by the animal most willing to obey the commands of a rabbit. -Robert Brault, writer (b. 1938)

"The common application of a sub woofer is far from high fidelity because of two things: The user turns up the volume to a level greater than his speakers, and turns up the crossover frequency to 90, 120, even 150 cycles. He does this because he is waiting to hear the sub work, and that is what it takes to get it to draw attention to itself. In this application, the response of the speakers are altered by overlapping them with a thick veil of bass."

I agree with with Steve's observations. If a sub is crossed over at say 80 Hz, as you increase the sub volume at some point the brain recognizes a disconnect between the volume of Sub frequencies below 80 Hz and Mains frequencies above 80 Hz.

On the other hand if one tries to overcome this problem by setting the crossover at say 150 Hz a second problem arises. Subwoofers by their very nature are designed to play Low & Loud and in my experience sound crappy when you attempt to cross them over at higher frequencies.

The HSU Mid Bass Module seems to solve both problems in my system. A unit optimized to reproduce frequencies between 50 and 150 Hz with accuracy and authority. No sense of "overlapping the main speakers with a thick veil of bass". The MBM simply adds to the music rather than drawing attention to itself.

I would look at the bottom end rolloff on your speakers, and adjust the sub accordingly... Maybe a mild 'suck-out' between the two, some overlap... Yes, crossing over to the sub too high introduces too much mid bass, which causes all sorts of phasing problems... That's why some subs have variable phasing...

Having had a sub previously, I'd keep the X-over low... And not want to 'hear' the sub... Also, the level on the sub should be rather low...

If a rabbit defined intelligence the way man does, then the most intelligent animal would be a rabbit, followed by the animal most willing to obey the commands of a rabbit. -Robert Brault, writer (b. 1938)

[b]"Can you expand on this? Any idea why a smaller sub would add more weight than the larger one?"[/b]

First thing, the HSU Mid Bass Module is not a subwoofer in the traditional sense. So to judge it's effectiveness as I have described based on it's size alone would be a BIG mistake.

Traditional subwoofers are designed and optimized to go low and loud. Generally that means bigger, heavier drivers and bigger enclosures as your question suggests. The sealed ULS-15 does a wonderful job of going low with accuracy.

On the other hand the Mid Bass Module does a wonderful job of doing what it was designed to do. Reinforce the 50 to 150 Hz range with accuracy. If you read some of Dr Hsu's explanations on the MBM he selected a light weight 12" driver and designed the enclosure specifically for the MBM application.

So the traditional Subwoofer and the Mid Bass Module are really two different animals. I will try to explain it this way. If you are primarily into music and want to reinforce the 85% of the bass material that lies between 50 and 150 Hz on most recordings then I have found the MBM to be very effective. If you are only interested in reinforcing the last 15% of the bass material that is below 50 Hz on most recordings then a subwoofer would be a better choice.

Sure, I have both and and they sound great together. I realize however not everyone will have that luxury. I have listened to both and IMHO it's not even close. If I had to choose between the two it would be the MBM.

"One of the implications of this aspect of human hearing is that you will perceive a progressive loss of bass frequencies as a given sound becomes softer and softer. For example if you are listening to a recording of an orchestra and you turn the volume down, you will find that the bass instruments are less and less prominent. This is the purpose of the so-called "loudness contours" on audio amplifiers; they allow you to boost the bass frequencies when you are listening at low sound levels to give you a more realistic balance of the high and low frequencies in the music."

If you go to the link and look at their graphs the frequencies between 50 and 150 Hz really take a hit (compared to higher frequencies) as volume is reduced. The Mid Bass Module reinforces that frequency range making listening at low to moderate volumes very satisfying.

If I recall correctly, the effect described of 'volume intensity relative to level', it has been supported by the Fletcher-Munson curves from the 1950's. I'm sure it is in our genes for a reason, but I still envy other animals' hearing. The sub that I used to own was a Velodyne UDL-15. I found that it was a great enhancement with the right speakers. The idea that a speaker cone was in constant 'check' in reference to the music signal seemed to be as good as it gets. But, as I stated, matched with the right speakers was important so that the two could be as seamless as possible. Driver distortion is unbelievably high in the lower regions of frequency, making less of a note and more of a thud as a rule.

"But, as I stated, matched with the right speakers was important so that the two could be as seamless as possible. Driver distortion is unbelievably high in the lower regions of frequency, making less of a note and more of a thud as a rule."

Since the Mid Bass Module is not a Subwoofer it does not seem to present the same challenges integrating with the mains. And the light weight 12" driver really pumps out the notes and not the thud.

Yes, and I agree with you also. It is a very good idea, using a less traditional sub that doesn't deal so much with unneeded frequencies. Correct bass reproduction, as hard as it can be to get right, is well worth it. Still, we have all visited those who have systems that they are so proud of because it can rattle windows....hmmmm to each his own I guess.

"Still, we have all visited those who have systems that they are so proud of because it can rattle windows....hmmmm to each his own I guess."

LOL !! Yea, we have all met that guy at one time or another.

My fasination with the HSU Mid Bass Module really centers around what it adds to the listening experience at low to medium volumes. This is where I listen 90% of the time and there are certainly no windows rattling.

If a rabbit defined intelligence the way man does, then the most intelligent animal would be a rabbit, followed by the animal most willing to obey the commands of a rabbit. -Robert Brault, writer (b. 1938)

Man, That's what I love about these issues. The different ideas that have been tried, some successfully. I never quit experimenting with sound. It still is important to me to be able to return to the original if I don't like what I hear. Bass is so special because of our rooms and taste. And sometimes I wish I had several systems to listen to in order to get what I want at that moment.

Looking at the spec on my m/l`s they go down to 40Hz. Not sure what the double bass is capable of but not ever having tried subs I`m sure I can hear well enough a long way down to the point where the air shift takes over and you get that `felt` pulse, even to the point where you think your ears may not take to kindly to low sonics.Given that my Decware amp gear is renowned for bass reproduction this means that they pass on the large wattage shift of some bass extensions by using very generous component specs so they dont get `swamped`.The band sound balance is a touchy subject if you`ve ever played live. Volume controls easily creep up if not kept an eye on by a third party aka recording engineers in studios or if a big band the control desk, PA, in live play. Ideally your finished recorded sound should be `just so`.Listening to G.Deads live double I cant help but ask the bass player to back off as it is very raw and transmits a lot of energy. Not comfortable but for `Dead heads` which I`m not. There are many similar recordings where bass `energy` is felt more than others.Live, the whole band will be very loud and in my experience the bass is not usually prominent, but is more the texture or floor that the rest of the band live in.Bad experiences, one or two : Humble Pie in S. Marriots home town Assenbly Hall. OMG the bass was dangerous. Windows were very loud, you could feel the blood draining as your chest was being thumped. It was total nausea and you really thought eardrums were at risk. Took some time to acclimatise.

Thanks again DBC for your insight with the Hsu mid bass module. It is a more efficient paper cone & driver motor too (by design as you eluded too)....to keep up with my Union Driver.

Out in the room, just a few feet away from my Listening Chair....is where I will start for placement. Anyway, after some time with my new Zu Unions and then the mid bass module I will return with some observations & pics. Party on Wayne - party on Garth.....-Stone of Tone

"Live, the whole band will be very loud and in my experience the bass is not usually prominent, but is more the texture or floor that the rest of the band live in."

Some of that depends on the band, music style, the acoustics of the live venue or recording if listening at home. I listen to a lot of Live Blues in local clubs and they tend to have the balance such that you can hear the individual bass notes as you watch the bass player pluck the strings.

I have been to more than a few live shows where the bass is more of a soup, not much bass note definition. On recordings some times the bass sounds more like a broth (thin and no defined notes).

The Mid Bass Module I've been using seems to have the ability to lift the individual bass notes out of the soup. Especially at low to moderate volumes where I do 90% of my listening.

For the last 4 days I have really been hooked on the Red Hot Chili Peppers. I've had these CD's for years but they were never my favorites. Now that I can hear all the individual bass guitar notes I have to say their bass player "Flea" really lays down a nice groove on all their songs.

Great thread and great info. One of things I noticed with the Anedio D2 Dac was how much more satisfying the music was at low volume levels. Same output volts as the other dac. More more weight and body. Recently I changed my source feeding the Anedio with a Bryston BPD-1 music player. Even more improvement. I now listen at lower volume levels and still feel the same weight and body. Both these units offer extremely low distortion levels and noise floor. Is that what accounts for what I am hearing?

If you place your cursor on each instrument shown on the bar chart it will display where that instrument falls on the Ear Sensitivity Chart to the right. I thought it was interesting how much cello, guitar and other instruments fall into the 50 to 150 Hz range where the ear is less sensitive, especially at normal or lower listening levels.

The other night I watched the Nirvana MTV Unplugged DVD at a moderate listening level. It was the first time I had clearly heard the young lady playing the cello. It was great and really added to the overall presentation.

My old Zen Select just never had the low end resolution as my new CKC does. Without the MBM on the cello is barely audible. With the MBM on it is clearly audible and distinct from the other instruments.

I find that to be a really good point. Low volume leaves out some information. On another related note, if I remember correctly, harmonics go both ways. So if there are harmonics from say a cello that reach beyond it's scale, then the obverse is true. And harmonics are weaker signal than the original.

Been meaning to post but been too busy listening or working. I've actually been getting up an hour early each morning just so I can listen for a bit. The Super Zen and Mid Bass Module combination have provided an audible window into what is really happening in the lower frequencies. This has allowed me to tweak the system some and actually hear the improvements.

Last week I changed to a different equipment rack I had on hand in an attempt to improve vibration control. In the process I found that my two sets of Decware 1/2 meter interconnects I had been using were a tad tight so I went to a couple 1 meter pair of pure silver interconnects I have had for a long time.

It was interesting, when I powered back up and started listening my first impression was the low end was just a tad thinner. After listening for a while it was apparent that the low end was not thinner but more accurate with more clarity. Kick drum and Bass Guitar notes for instance seemed to have more space between them. Less tendency to bleed together.

Now to your question. Per Steve Deckert's advice I use the speaker level connections so that the MBM is reproducing as close as it can the signature of the Super Zen amp. I'm actually using common Cat-5 computer network cable purchased from Lowe's. I know, does not sound very Hi-Tek but it sounds good. The cable has four twisted pair, each individual conductor is solid copper (not stranded). I always use bare wire speaker level connections at the amp, mains, and MBM. The solid copper conductors hold up better than the very fine stranded type.

I twisted two of the pair together for the POSITIVE and the other two pair for the NEGATIVE. So basically I have one Cat-5 cable for the left channel and one Cat-5 cable for the right channel. I have a pair of MBM's so I run them in Stereo, left channel only to left MBM, right channel only to right MBM.

I have experimented with just one MBM where I run both speaker level channels into a single MBM and the single unit performs very well in my room. The MBM has speaker level input connectors for both left and right channels. It did seem when I switched back to dual MBM's (Stereo) that low end clarity was improved a bit but it was not a night and day difference. I have implemented a few other small system tweaks since then that might account for the difference at that time ??

I did have a small ground loop issue. I run dual MBM's and ULS-15 subs in stereo mode. So left channel for instance I run speaker level connection to the left sub and daisy chain to the left MBM. Seems the MBM's would interact with the sub it was mated to. I simply ran a Radio Shack test lead with alligator clips on each end from one of the steel toggle switches on the MBM to one of the toggle switches on the ULS-15 sub to give them a common ground.

I talked to Dr. Hsu about the ground loop. Basically they expect anyone not living in a cave these days will use the line level connection. I think they expect the ground on the line level interconnect to tie all the grounds back to the amp ??

After I got my Super Zen I could just barely hear a very low level hum with the MBM's turned ON. I had to be right up next to the mains to hear this. Not audible at the listening position or with the MBM's turned OFF. I tied the the ground jumpers installed between each MBM and sub back to the case of my surge protection device where everything is plugged into. Bam, everything was dead quiet and it made a noticeable improvement in low frequency playback. Again just seemed to be a little more separation and space between instruments on the low end.

It seems if you have any type of low level distortion from your source, pre or amp the MBM is going to make that audible. In my case that has been a good thing since I have been able to identify (hear) and address these things.

The biggest advantage of the MBM is that you achieve big, full, spacious, satisfying sound at low to moderate volumes. I've been trying for 20 years to achieve this type of sound in a listening room with subwoofers and have had limited luck at best. The MBM is not a subwoofer.

I've come to appreciate that subwoofers are more of a Sledge Hammer. They are designed to reproduce frequencies that you feel more than you hear. The MBM is more of Hammer, much more nimble, more subtle.

Thanks for that info! I think if I were to use these I'd use the line level inputs from the CSP2+ . . . I will even have one of those with an extra stereo out put which would work for two or one. I like the signature of the CSP2+ so much that thanks to Bill selling one here I bought another to use with my SACD player which doesn't sound quite as good just straight into the Torii Mk III. For me the ideal preamp is a CSP2+ with three or four inputs. . . .

Anyway, your experience is really informative and I have no doubt that you are enjoying excellent sound. I'm moving to a townhome in OHio soon and will have a few neighbors; I've been living in a house with some space between neighbors for twenty plus years. I may need to listen at lower volumes, and your experience shows these HSU units can be a big benefit.

I've been following this forum for over 12 years now (since I purchased my original Zen Select). As you know I don't post much, I come here primarily to see what I can learn from folks like you. Thanks to everyone who frequents here and shares.

There are not many Mid Bass Module online user reviews to be found. The few I have managed to find have all been very positive. I know I was slow to try one myself because of all the difficulty I have experienced over the years trying to integrate a subwoofer into my music system.

Best advice I can give when it comes to the HSU Mid Bass Module:

1) Just forget everything you know or think you know about subwoofers.

2) The Mid Bass Module is not a subwoofer therefore refer to rule #1.

I hope you have a chance to try one some time. My guess is it would sound great on your CSP+ line level outputs. I have an older CSP and do not have that option.

I wish Steve would make the CSP+ available in the same black metal chassis as the Super Zen, I would probably upgrade that also. Call me crazy but I just like the Old School 50's style of the metal chassis.

Another thought: I really like the simplicity of the HSU products. None of the "Digital Signal Processing", "Servo Control", "Parametric Equalization" or any of that other CRAP that I have tried with only limited success at best.

Who would have Thunk It, simple amp, driver and enclosure that does exactly what they say it will do.

Well, I've never liked systems I've heard with subwoofers, admiittedly they were dvd based not music, but I just never bothered to learn about them in two channel use although there were years when I could have used them and would have really enjoyed them I bet.

These modules attract me because a) they're NOT subwoofers and b) they address a frequency band that really can be anemic in some rooms especially at low to medium volume and d) YOUR information and assessment of them in a Decware system and how well you've explained them and described the system as a whole.

I trust YOU and your ears more than many online reviewers I might find. They seem to be a really interesting and innovative product, which as you know Decware people know how to identify and enjoy.

As for the CSP2. . . My CSP2 now in use in my bedroom system I asked Steve to build in the black chassis to match my then in use SE34 Monoblocks in the same Decwware chassis. It's a 2 and not a 2+ so no mono output or other outputs besides the main stereo one, and I had him make it without the headphone jack because I just don't do headphones--Steve said it would sound a bit better without the jack. So I know that it's POSSIBLE to get a 2 in that chassis. Now a 2+ . . . . probably would be more difficult, but you know Steve, the more difficult just takes an epiphany.

Anyway, the HSU modules are very intriguing and I appreciate you bringing this exposure to them. I may just have to try them out myself in the future.

Just as my Zen Select and Klipsch RF-7s were a lens into the mid and upper frequencies 12 years ago, The Super Zen with HSU Mid Bass Modules have been an equally impressive lens into the lower frequencies. The Zen Select just sounds muddy in the low end by comparison.

With the new combination I have been able to hear step by step improvements as I solve minor grounding issues, address vibration and experiment with cables. I have to say I just did not think this type of bass clarity was possible in a 15'x21' listening space.

All those Hendrix, Joplin, Jefferson Airplane, etc. CD's that always sounded a bit thin on the bottom end have new life. It's amazing how much subtle bass guitar is on all this material. With the accuracy & clarity of the Super Zen the MBM's have the power and speed to reproduce drums and bass guitar so that they are distinct and separate (no mud, no boom).

Last night I listened to the same Doors CD 3 times back to back. Just seems to have so much more pace, rhythm and body ???? I'm at a point where I can just set the volume at a moderate level and listen all day long. Don't feel like I have to tweak amp volume, MBM volume or anything on different songs. It's great when an upgrade like this comes along and suddenly your entire CD collection is a completely new experience.

Well put DBC, like you, I have been part of this Foum for 12 years with the purchase of my Zen Select SE84CS in May of 2001. I don't post that much either and I learn things from Poster's like Lon, whom I very much appreciate on this Forum.

Now, I'm learing from you. I am ordering a MBM soon as I finish this post! Furthermore, I have a pair of Klipsch RF 52 II coming on Monday from Crutchfield. $448.98 delivered....can't complain. I have bought them for my bedroom system. However, after a long breakin...I think they will make it in for an audition in the Listening Room System.

Anyway, back to the MBM....RF 52's come Monday and the MBM by the end of next week and I'll return with some early thoughts.

I will use the MBM-12 MK2 in my Listening Room System first...and then out with the Polk 1.2 bohemoths...then with the Bedroom System....burned in RF 52 II's down the road.

I will be purchasing just one (1) MBM...I do realize you have two. I will run 14 gauge wire to them from Super Zen CKC Speaker connections to Speaker connections of MBM....placing the MBM near me/Listening Chair.

Stone, I'm pretty sure you will love those Klipsch. I gave my brother my old (1 yr. ) pair of rb81's to help out in his system. I loved them...great bang for the buck and Crutchfield is a great co. to buy from.

I think you will find a single MBM to be effective. I have experimented with a single MBM in my room and it does a very nice job.

I have never experimented with the MBM placed close to the listening position as HSU suggests. I can see this being effective for Home Theater but not so sure about Music ?? Two potential issues; First being localization (hearing sound coming from the MBM), and Second the potential for phasing issues between the mains and MBM ??

I found after months of experimentation that the MBM sounds best in my system with the MBM crossover set at the max 150 hz setting. The MBM is actually playing over (augmenting) my RF-7 mains that go down to 50 hz. This being the case I would think the best MBM location for music would be somewhere between the mains to avoid potential phasing issues (holes in the mid-bass region) ??

I look forward to your findings since I have not experimented with near field placement.

Just a reminder this is NOT a Subwoofer (for anyone skiming the thread):"The MBM-12 MK2 woofer is optimized for mid to upper bass reproduction - a very light cone, low inductance voice coil, and a strong magnet yields extremely quick response with high efficiency. It demonstrates excellent micro-dynamics and an extremely wide dynamic range that no single subwoofer can provide".

marky: good point since it is down firing....I will throw a piece of plywood under it after hearing it first off the carpet.

might be a bonus Stone, I was just getting my front firers off the floorboards, nothing to do with subs...then I thought, a few slabs on top of a sub might... :)The MBM sounds interesting. When you dont use subs you think you have weight and body enough. Detail of mid lows and up from a unit (not sub) well you know, it`s allways interesting to find out what lies hidden and can be brought out without comprimise. Looking forward hearing of your trials, following DBC`s good low down on them.